Method and device for withdrawing suspended microparticles from a fluidic microsystem

ABSTRACT

A method of discharging a fluid flow with suspended microparticles from a fluidic microsystem ( 10 ) is described, whereby the fluid flow converges with at least one output flow to form a discharge flow at the end of a discharge channel ( 14 ) of the microsystem, and the discharge flow is delivered through a conduction element ( 19 ). A microsystem with a flow output device for implementation of this method is also described.

[0001] This invention relates to a method of discharging suspendedmicroparticles from a fluidic microsystem, in particular for dischargingthe microparticles from the microsystem, and a method for meteringand/or treating of a microparticle flow output from a fluidicmicrosystem. This invention also relates to a microsystem designed forcontrolled discharge of suspended microparticles, and a discharge devicefor discharging suspended microparticles from a microsystem.

[0002] Fluidic microsystems for manipulation of biological or syntheticmicroparticles are known in general. The microsystems usually includeone or more input channels, a channel arrangement for receiving and/orguiding fluids with suspended microparticles (e.g., biological cells)and one or more output channels. The channel arrangement has typicaldimensions in the submillimeter range, e.g., approx. 100 to 500 μm. Thesuspended microparticles are characterized and/or manipulatedelectrically and/or optically, for example, in the channel arrangement.The suspension liquid with the microparticles has a freely adjustableflow velocity in the channel arrangement, which depends in particular onthe manipulation and/or characterization steps implemented. Typical flowvelocities are in the range of 10 mm/s or less. In conventional systems,connecting lines (so-called tubing) are connected to the output channelsas the ends of the actual microsystem, in which connecting lines themicroparticles are discharged from the respective outlet channel forfurther processing or collection or the like. These connecting linestypically have a length of approx. 2 to 8 cm. This corresponds toapprox. 1 to 4 μl at an inner diameter of 254 μm, for example. A cellhas essentially the same velocity in a connecting line as inmanipulation in the channel arrangement and thus it needs a transit timeof approx. 3 to 60 minutes from the outlet of the microsystem to the endof the connecting line, depending on the pump rates.

[0003] Such high transit times are unfavorable for reproducible furtherprocessing of the suspended microparticles. For example, considerablyshorter times of approx. 10 to 60 seconds are needed for confirmedsingle-cell separation, as required for cloning cells. In addition,sedimentation phenomena which also play a role definitely reduce thecell recovery rate when the transit time is too long.

[0004] Rapid and reproducible discharge of suspended microparticles frommicrosystems, metering and/or treating of the oncoming flow ofmicroparticles in transmission into subsequent systems is a problem thathas not previously been solved at a justifiable technical expense.

[0005] The so-called enveloping flow principle of hydrodynamic focusingis known in fluid technology. Hydrodynamic focusing permits an alignmentof specimen particles and, for certain analytical and preparative tasks,it allows particles and cells to be isolated (see A. Radbruch in FlowCytometry and Cell Sorting, Springer Verlag, Berlin 1992). Forimplementation of the enveloping flow principle, a fluid flow with theparticles is surrounded by an outer enveloping flow in a coaxial nozzledesign. The enveloping flow must have a much greater velocity than thefluid flow so that hydrodynamic focusing may take place. The flowvelocity of the enveloping flow is typically several thousand timesgreater than the flow velocity of the fluid. The fluid flow is entrainedby the enveloping flow. The use of hydrodynamic focusing is limited tomacroscopic laboratory equipment. It is not applicable in microsystemtechnology because due to the required high velocity of an envelopingflow, the flow conditions in the microsystem would also be influencedupstream relative to the aforementioned nozzle design. However, such anexternal and non-reproducible interference in flow conditions in thechannel arrangement of a microsystem is not desirable.

[0006] Furthermore, there are known microstructured flow switches whichare based on the enveloping flow principle (see G. Blankenstein in thepublication “Microfabricated flow system for magnetic cell and particleseparation” in Sci. & Clin. Appl. Magn. Carriers, eds. Häfeli et al.,Plenum Press, New York, 1997). With a flow switch 10′ a specimen flow Pis accompanied by a separate enveloping flow H in the channelarrangement of a microsystem, e.g., in a separation section 12′, asillustrated in FIG. 7. A magnetic separation device 11′ is provided onseparation section 12′. Several outlet channels 14′ are connected to theseparation section 12′, certain fractions of the specimen and envelopingflows being directed into these channels, depending on the function ofseparation device 11′. Use of the flow switch is limited to fluidconvergence flows or fluid separations in the interior of themicrosystem. The dimension of the output channels determines theparameters of the specimen and enveloping flows that can be added. Theabove-mentioned problem of discharging the suspended microparticles frommicrosystems cannot be solved with a flow switch.

[0007] The centering or deflection of a specimen flow is implementedwith hydrodynamic focusing and the above-mentioned flow switches.However, the above-mentioned problem of extracting or focusingmicroparticle suspensions at the outlet of microsystems, i.e., inparticular at the interface with macroscopic systems, is not solved inthis way.

[0008] The object of the present invention is to provide an improvedmethod and a suitable system for discharging suspended microparticlesfrom a fluidic microsystem, which in particular is robust, has a simpledesign and guarantees rapid discharge of particles without any negativeeffect on the function of the microsystem, in particular the flowconditions prevailing there, and can be adapted easily to differentapplications. This invention attempts in particular to achieve adischarge of microparticles with a fluid flow from microsystems ormicrocapillary systems with little or no loss of microparticles.

[0009] The object of this invention is in particular also to influencethe properties of the suspension removed or separated when dischargingsuspended microparticles. The suspension is to be altered with regard toits physical composition and/or with respect to the particle density(dilution). The object of this invention is thus also to provide amethod of adjusting the particle density in a suspension output from amicrosystem for metering of the suspension output. Additional objects ofthis invention include providing microparticles and treating amicroparticle flow that has been output.

[0010] These objects are solved by a method and devices having thefeatures according to claims 1, 12 or 25. Advantageous embodiments andapplications of this invention are defined in the dependent claims.

[0011] The basic idea of this invention consists of creating a method ofdischarging a fluid flow with suspended microparticles from a fluidicmicrosystem in which the fluid flow is combined with at least one outputflow at the end of an output channel of the microsystem to form adischarge flow which is then discharged as a total flow. In contrastwith the conventional techniques of hydrodynamic focusing and the flowswitch, the discharge flow is formed after manipulation and/orcharacterization of the suspended microparticles in a microsystemwithout influencing the flow conditions in it. The discharge flow isdelivered through a suitable conduction element (e.g., tubing, pipelineor the like) with characteristic dimensions which are adapted to theparameters of a component to accommodate the discharge flow (e.g., ameasurement, storage or manipulator device).

[0012] The method of discharging the fluid flow is a metering (dosing)method in which the density of the microparticles and their provision atthe end of the conduction element are adjusted in a predeterminedmanner. This invention makes it possible for the first time to adjustthe velocities of flow required in operation of a fluidic microsystemfreely and independently of one another. In the microsystem, there is arelatively low flow velocity of the microparticle suspension (seeabove). After output from the microsystem, the flow velocity should beincreased in a certain manner, depending on the application. In contrastwith the enveloping flow principle of hydrodynamic focusing, thevelocities of flow of the fluid flow and the output flow have comparablevalues. The flow velocity of the output flow may be lower than, the sameas or greater than the flow velocity of the fluid flow. However, no suchgreat differences in velocity are established as in focusing (e.g.,factor off a few thousand or more). In typical applications, thequotient of the velocities of flow of the fluid flows and output flowsis in the range of 0.1 to 500, preferably less than 300. The inertia ofthe suspension dosage according to this invention in such flow ratios ispreferably especially low. The particle-free volume of the output flowis adjustable individually especially after each individualmicroparticle has passed by with the fluid flow. The particle sequencein the fluid flow typically includes one microparticle in a time rangeof approx. 100 ms to 1 s. Such time ranges make it possible to adjustthe flow velocity of at least one output flow. Depending on the taskinvolved, individual particles can be removed from the microsystem morequickly or more slowly. Thus, a problem in microsystem technology whichhas been unsolved in the past has now been solved for the first time.

[0013] To produce the output flow, according to a preferred embodimentof this invention, a flow output device having at least one outputchannel is used, opening at the end of the discharge channel of themicrosystem. Preferably several output channels are used, these channelsbeing guided from different directions to the fluid flow. The mostimportant object of the at least one output flow consists of the fluidicaddition of a predetermined amount of liquid to the fluid flow at theend of the microsystem. By adjusting the flow rate of the output flow(volume throughput per unit of time) the specimen volume at the outletof the microsystem can be adjusted as desired. Preferably at least oneoutput flow is formed, its flow velocity being lower than the flowvelocity of the fluid flow and its pump rate being greater than the pumprate of the fluid flow. According to this invention, a dilution of thefluid flow is provided at the outlet of the microsystem.

[0014] According to another function, the at least one output flow alsoserves to treat the suspended microparticles. To do so, the output flowis formed by at least one treatment solution, e.g., a washing solution,a culture medium or a conservative solution. Preferably multiple outputchannels are provided for guiding various treatment solutions fromvarious directions which are combined with the fluid flow at the sametime or successively downstream.

[0015] In an alternative embodiment of this invention, the pump rate ofthe output flow is adjusted so that its flow velocity has a definedvalue and is greater than the flow velocity of the fluid flow. In thisembodiment, the flow output device itself may be used as a pump devicefor adjusting the flow conditions in the microsystem, replacing orrelieving the pump devices in the channel arrangement of themicrosystem.

[0016] An object of this invention is also a fluidic microsystem havinga channel arrangement for receiving and/or flow-through of fluids withsuspended microparticles and at least one discharge channel for guidinga fluid flow in which at least one flow output device having at leastone output channel for guiding an output flow, opening at the end of thedischarge channel, is provided at the end of the discharge channel.

[0017] The mouth of the at least one output channel at the end of themicrosystem discharge is preferably designed so that the fluid flows andoutput flows converge. A conduction element, e.g., in the form of a tubeor a pipe at the end of which may be provided at least one additionalflow output device having additional output channels for furtherdilution of the discharge flow, is connected at the downstream end ofthe flow output device.

[0018] According to a preferred embodiment of the microsystem, the atleast one output channel forms a side influx which opens into thedischarge channel or at the end of the discharge channel. Since there isno focusing of particles, it is possible with advantage to omit thering-shaped influx which is formed in hydrodynamic focusing and insteadto provide a planar embodiment of the channel structure. There areadvantages in particular with respect to the simple design andminiaturizability of the flow output device. When multiple outputchannels are provided, they are preferably also arranged in one plane aslateral influxes. Several flow output devices can also be arrangedasymmetrically and/or offset with a distance from one another in thedirection of flow, depending on their tasks.

[0019] According to another embodiment of this invention, themicrosystem is equipped with a measurement or storage device arranged atthe flow output device of the microsystem. A titer plate or a cellculture plate, for example is provided as the storage device.

[0020] A subject of this invention is also a flow output device fordischarging suspended microparticles per se, which can be placed at anoutlet of a fluidic microsystem for flow dilution of the fluid flowcoming out. Flow dilution is understood to refer to the reduction inparticle density in the fluid flow running during the flow by combiningit with one or more output flows.

[0021] An important feature of this invention is that the dosage of theoutput fluid flow is based on the manipulation and/or characterizationof the microparticles in the microsystem. In contrast with allconventional enveloping flow techniques, manipulation and/orcharacterization, such as dielectrophoretic treatments using dielectricfield cages or field barriers, displacements or measurements withoptical forces (optical tweezers), electrophoretic or electro-osmoticprocesses take place before the fluid flow converges with the at leastone output flow. For example, first the microparticles are separatedspatially using essentially known field barriers and are worked up inthe channel arrangement of the microsystem. The microparticles aremeasured at the respective positions. Releasing the field barrierscauses the microparticles to be removed through the discharge channelwith the flow velocity in the channel arrangement, i.e., at a relativelylow transport velocity. Although the low transport velocity is desirablein the microsystem, e.g., to fill up the dielectric field cages, thetransport velocity (flow velocity) established in the flow output deviceis elevated, depending on the application. Due to the output flowsupplied, it is advantageously ensured that the microparticles tested ina separated state will still remain separated even after manipulation ormeasurement, with no losses occurring and short transport times beingachieved. This offers special advantages in manipulation of biologicalcells and especially in depositing of single cells.

[0022] This invention offers the following advantages. Due to the use ofan output flow at the outlet of a microsystem, the suspendedmicroparticles, e.g., biological cells or cell constituents, syntheticparticles or composite particles with biological and syntheticcomponents, macromolecules or aggregates of macromolecules can beremoved from the microsystem with little or no loss. The flow rate inthe output flow can be increased without any interfering influence onthe flow velocity in the microsystem upstream from its outlet. Due tothe increase in the flow velocity of the particle suspension afterdischarge from the microsystem, the risk of interactions between theparticles and the channel walls is reduced. For example, cell adhesioncan be prevented. This invention is applicable to advantage especiallyat low velocities of flow in the microsystem in the range of 1 μm/s to10 mm/s, for example. According to this invention, the velocity of theparticle suspension in discharge from the microsystem can be increasedas greatly as possible for effective and rapid discharge of theparticles from the microsystem. For example, a peristaltic pump issuitable for this purpose. In one example, the velocity of thesuspension could be accelerated from 1-20 μl/h to 70 to 280 μl/h. Athigher velocities of flow, however, pulsation of the peristaltic pumpacts on the flow of the particles upstream from the flow output device(e.g., disturbance in maintaining the microparticles in dielectric fieldcages).

[0023] Use of a hydrodynamic pump principle is more suitable for rapiddischarge of the particles. For example, the liquid may be sent to theflow output device from a liquid-filled reservoir which is acted upon ata low excess pressure applied via a compressor with a throttle valveconnected to it. Thus, much higher flow rates, namely up to 25 μl/s(with a working range of up to 0.8 bar excess pressure), or typically 2μl/s (with a working range of up to 0.1 bar excess pressure) can beachieved in the microsystem without any negative effect on the incomingparticle suspension.

[0024] However, there is also a reduction in the suspension density.This reduction in suspension density is to be differentiated from theparticle alignment in hydrodynamic focusing. After manipulation and/orcharacterization of individual microparticles in the microsystem, theyare already aligned in a row at the outlet or otherwise separated.However, the reduction in suspension density means that fluid quantitiescontaining one or a few particles, e.g., in the form of drops, can beprovided, such that their volume is adapted to the receiving volume of aconnected measuring device. A predetermined drop size may be formed atthe end of the conduction element downstream from the flow outputdevice, which is advantageous for single-cell deposition.

[0025] A reduction in suspension density also permits more generoustolerances in fluid coupling. When dead volumes develop in the dischargeflow in particle manipulation in the microsystem, e.g., as a result ofsorting processes, they are compensated by the dilution of thesuspension.

[0026] Another important advantage is in the addition of treatmentsolutions to the fluid flow. The treatment solution may be used with amuch greater volume in comparison with the suspension volume in themicrosystem. Different output flows may consist to advantage ofdifferent treatment solutions and may optionally be supplied atdifferent flow rates. The treatment of the microparticles discharged canbe adjusted quantitatively.

[0027] The flow output device according to this invention can be adaptedeasily to any microsystems because there are no restrictions with regardto the geometry of the convergence of the fluid flow and the outputflow. In particular, it is not absolutely necessary for the fluid flowto be completely enveloped by the output flow. Also, no focusing of themicroparticles in the discharge flow is necessary.

[0028] To achieve the flow dilution according to this invention, theflow velocity of the output flow can be set so low with a suitable crosssection of the output channel so that essentially there is no feedbackeffect on the microsystem.

[0029] This invention can also be used with microsystems in which thereis no net flow in the microsystem or it is negligible, and themicroparticles are moved through the channel arrangement by electric ormagnetic forces.

[0030] Additional details and advantages of this invention are describedbelow with reference to the drawings, which show:

[0031]FIG. 1 an embodiment of a microsystem according to this inventionequipped with a flow output device;

[0032]FIG. 2 a top view of a flow output device according to thisinvention;

[0033] FIGS. 3-6 top views of other embodiments of a flow output deviceaccording to this invention; and

[0034]FIG. 7 an illustration of a conventional flow switch in a fluidicmicrosystem.

[0035]FIG. 1 illustrates in a schematic top view components of a fluidicmicrosystem 10 having a flow output device 20 which is designed forimplementation of the discharge of suspended microparticles from themicrosystem by the method according to this invention. The term fluidicmicrosystem is understood to refer here in general to a device having atleast one input, one channel arrangement for receiving and/or guiding afluid, in particular a particle suspension, and at least one outlet.Liquid lines extending through the channel arrangement between theinlets and outlets have geometric designs, dimensions andcross-sectional shapes depending on application. The liquid lines aredesigned, for example, as structured channels in a solid-state carrier(chip), e.g., made of a semiconductor material or a plastic. The channelbottoms are formed by the chip material and the channel covers areformed by a suitable chip cover, e.g., made of glass or plastic.However, it is also possible for the side walls of the channel to beformed by spacers which are suitably shaped and project from asolid-state carrier. Furthermore, microelectrodes may be provided in thefluidic microsystem to form high-frequency electric fields fordielectrophoretic manipulation of the particles, and manipulationdevices such as electroporation electrodes, pump devices and measuringdevices may also be provided. These components are known per se frommicrosystems technology and therefore need not be explained in detailhere.

[0036] Typical dimensions of the channel arrangement of the microsystemare less than 800 μm, preferably 500 μm (channel width) and less than200 μm (channel height).

[0037] In the embodiment of this invention illustrated in FIG. 1, thefluidic microsystem 10 and the flow output device 20 are providedtogether on a substrate through a spacer 17 forming the channel walls.As an alternative, it is also possible to design the microsystem 10 andthe flow output device 20 separately from one another as modular units(see below).

[0038] The microsystem 10 has two inlets 11 a and 11 b which areconnected to a main channel 12, which generally represents a systemfunction-specific channel arrangement. The main channel 12 is divided atthe end into a drain 13 (so-called waste channel) for dischargingunwanted or separated fluid and/or microparticle components and adischarge channel 14. The suspension with the desired microparticles,which are to be transferred from the microsystem to a connectedcomponent for receiving the output flow, e.g., a measurement unit,storage unit or manipulation unit, is guided in discharge channel 14.Therefore, the flow output device 20 is provided at the end of thedischarge channel 14.

[0039] The flow output device 20 has two output channels 16 a, 16 b,each extending from an output flow inlet 18 a, 18 b to the end of thedischarge channel 14. The output channels 16 a, 16 b open at the end ofthe discharge channel 14 in such a way that the respective directions offlow in the discharge and output channels form an angle smaller than90°. After the mouth, the output channels 16 a, 16 b develop into aconduction element 19 which ends at an outlet 15. The arrangement ofoutput channels 16 a, 16 b, which is also known as a double-hornarrangement, is characterized by a mirror-symmetrical arrangement of thecurved output channels 16 a, 16 b with respect to the lengtheneddirection of flow at the end of the discharge channel 14.

[0040] The channel structure 10, 20 is also equipped with pump devices(not shown), which ensure a fluid transport in the microsystem 10,discharge of unwanted fluid through the drain 13, transport of outputflows through output channels 16 a, 16 b and discharge of the dischargeflow formed from the output and discharge flows through conductionelement 19 to outlet 15. These pump devices are known per se andinclude, for example, peristaltic pumps, spray pumps orelectro-osmotically active fluid or particle drives. Further examplesinclude pump devices based on hydrostatic pressure.

[0041] The channels in the microsystem according to this inventiontypically have channel heights of approx. 20 to 50 μm and channel widthsof approx. 200 to 800 m. The set velocities of flow in the channels arepreferably in the range of 50 to 1000 μm/s, corresponding to a pump ratein the range of 1 to 20 μl/h. The output channels 16 a, 16 b have largercross-sectional dimensions than discharge channel 14. The channel widthis typically in the range of 5 μm to 500 μm.

[0042] Microsystem 10 according to FIG. 1 is operated as follows. Themicrosystem 10 is used, for example, to separate suspendedmicroparticles as a function of their ability to react to a certainsubstance influence (e.g., an antibody). A fluid with the microparticlesto be separated or a solution with an active ingredient is added throughthe inlets 11 a, 11 b. In the main channel 12, there occur aninteraction between the microparticles and the active ingredient and theactual separation operation. The separation operation includes, forexample, the following steps. First, the microparticles are separatedand aligned by using field barriers which are known as such. Then ameasurement is performed on the individual microparticles, e.g., ameasurement of the dielectric rotation. Depending on the result of themeasurement, a field barrier at the end of the main channel 12 isconfirmed to deflect the microparticles into the drain 13 or thedischarge channel 14. In discharge of the microparticles from thedischarge channel 14, with the traditional systems there is the problemthat the transport velocity remains unchanged at a low level; thisproblem is solved here by operation of the flow output device 20.

[0043] In the flow output device 20, in the output channels 16 a, 16 b,from the inlets 18 a, 18 b to the end of the discharge channel 14 outputflows are made to flow at a higher pump rate in comparison with thefluid flow in the discharge channel 14. The fluid flow is merged withthe output flows to form a discharge flow. The discharge flow conveysthe microparticles from the discharge channel 14 to the outlet 15 of theconduction element 19. Due to the output flows thus supplied, adhesionof microparticles to the edge of the conduction element 19 and theirsedimentation are prevented. Microparticles arriving at the end of thedischarge channel 14 are conveyed reliably and at a predeterminedvelocity to outlet 15. This facilitates in particular the deposition ofmicroparticles in the reservoirs of a cell culture plate.

[0044] An additional tubing or hosing element in which the entiredischarge flow composed of fluid flow and output flow is conveyed can beconnected to the outlet 15 of the flow output device 20 without theaforementioned adhesion or sedimentation problems occurring.

[0045] The entire discharge flow composed of fluid flow and output flowis supplied with a defined suspension density. Quantities of fluidhaving one or more particles, e.g., in the form of drops, leave at theoutlet of the output device or the tubing element. The volumes of thesefluid quantities can be adjusted to the requirements of a downstreammeasurement or storage device with the flow output device. For example,the fluid quantities (drops) are separated and deposited on a titerplate of a high-throughput screening system. Single-cell separation ispreferably achieved. As an alternative, the cells may also be separatedand deposited on a cell culture plate as the storage device.

[0046]FIG. 2 shows another embodiment of the flow output device 20 inthe “double-horn”-arrangement. In the discharge channel 21 of themicrosystem 10 (not shown here), microparticles 21 a are transported inthe direction of the arrow. Output flows 24 flow according to thedirection of the arrow shown here from the output flow inlets 22 a, 22 bthrough the output channels 25 a, 25 b opening at the end of thedischarge channel 21. The output flows 24 are generated with aperistaltic pump, a spray pump or a pump device based on hydrostaticpressure. They entrain the particles 21 a at the end of the dischargechannel so that they are guided to the outlet 27 through the conductionelement 26. The outlet 27 of the flow output device 20 is preferablyarranged at the point of intersection of the converging output flows 24.In the symmetrical channel alignment, this corresponds to a position ona reference line which corresponds to the alignment of the dischargechannel 21.

[0047]FIG. 3 shows a modified embodiment of the flow output deviceaccording to this invention. The flow output device 30 at the end of thedischarge channel 31 has only one output channel 34 leading from aninlet 33 to the outlet 32 of the conduction element 35. As in theembodiments described above, the fluid flow from the discharge channel31 also converges with the output flow in the output channel 34 in thisasymmetrical design. The microparticles contained in the fluid flow areentrained in the common discharge flow and lead to the outlet 32. It hassurprisingly been found that even with this asymmetrical design,adherence of microparticles to the wall of the conduction element 35 isprevented.

[0048]FIG. 4 illustrates another example of a “double-horn”-arrangement,although in contrast with the embodiment according to FIG. 2, this onehas an asymmetrical design. The flow output device 40 at the end of thedischarge channel 41 has a first output channel 42 a with a narrowchannel cross section and a second output channel 42 b with a widechannel cross section leading from inputs 43 a, 43 b to outlet 46 viaconduction element 45, respectively.

[0049] Reference number 44 denotes the output flows which are formedasymmetrically with respect to the pump rates and the geometry of theconvergence with the fluid flow from the discharge channel 41.

[0050] Due to the asymmetrical design according to FIG. 4, the inflow ofcertain treatment substances is further modified with the output flows44, as is also possible in the embodiments explained above, with respectto the substance quantities or directions of inflow of the output flow.For example, the quantity of treatment substance added to one outputflow can be varied as a function of the measurement or operating stateof the microsystem 10 (see FIG. 1).

[0051]FIG. 5 illustrates another embodiment of this invention in aschematic top view in which two series-connected flow output devices 50a, 50 b are provided. The flow output devices 50 a, 50 b are situatedone after the other in the direction of flow. The first flow outputdevice 50 a is situated at the end of the discharge channel 51 and isprovided with the inputs 53 a, 53 d and the curved output channels forguiding the output flows 54 a, 54 d. The second flow output device 50 bis mounted at the outlet of the conduction element 55 a. The second flowoutput device 50 b also includes curved output channels from inlets 53b, 53 c to guide the output flows 54 b, 54 c. The output flow formedfrom the fluid flow and the output flows is delivered via the outlet 52.

[0052] In the embodiment according to FIG. 5, various treatmentsolutions, culture media or conservative solutions may be suppliedthrough the individual output channels. The design according to FIG. 5may also be asymmetrical or through modified opening of the outputchannels. The output channels may be provided, for example, according tocertain positions on conduction elements 55 a, 55 b to supply thetreatment solutions according to a defined protocol.

[0053]FIG. 6 shows an example of modification of the opening of theoutput channels. By analogy with FIG. 5, two series-connected flowoutput devices 60 a, 60 b are provided, the first having two outputchannels arranged in the same position with respect to the direction offlow. In the case of the second flow output device 60 b, the outputchannels are arranged so they are offset relative to one another in thedirection of flow. The distance between the lateral influxes is in theμm to mm range, for example.

[0054] A channel structure for implementation of this invention may bemodified in a variety of ways in comparison with the embodimentsexplained above. For example, a flow output device for dischargingsuspended microparticles may be provided as a separate component, thedevice being mounted on the discharge channel (e.g., 14, see FIG. 1) ofa microsystem. A flow output device has dimensions of approx. 1 to 20 mmand can thus easily be set up manually without requiring suitable means,e.g., tweezers. For example, sealed connectors made of plastic or thelike may be provided for the connection between the flow output devicecomponent and a microsystem chip.

[0055] In deviation from the shape of curved output channels illustratedhere, other straight or curved channel designs may also be provided. Theoutput flows may also disembogue at the end of the respective dischargechannel in a plane different from the fluidic microsystem. In the caseof microsystems having multiple output channels or at the end of theoutlet of a microsystem, flow output devices according to this inventionmay also be mounted. Additional possible modifications are derived withrespect to the size and the flow parameters of the flow output device,depending on the application.

[0056] According to this invention, with the embodiments describedabove, it is possible for additional devices for particle and/or fluidmanipulation to be arranged in the conduction element of a flow outputdevice (e.g., conduction element 19 in FIG. 1). These devices include,for example, additional electrodes for developing electric fields in thesuspension flow in the conduction element. Electroosmotic flows can beinduced or electrophoretic particle separation can be performed in anessentially known way with the electric fields. In such embodiments,instead of one outlet (e.g., outlet 15 in FIG. 1) several outlets mayalso be provided as discharge elements for separated particles and/orflows at the end of a conduction element.

[0057] The features of this invention disclosed in the precedingdescription, as illustrated in the drawing and characterized in theclaims may be relevant either individually or in any desired combinationfor implementation of the invention in its various embodiments.

1. A method of discharging a fluid flow with suspended microparticles(21 a) from a fluidic microsystem (10), characterized in that the fluidflow is merged with at least one output flow to form a discharge flow atthe end of at least one discharge channel (14, 21, 31, 41, 51) of themicrosystem, and the discharge flow is delivered through a conductionelement (19, 26, 35, 45, 55 a, 55 b).
 2. The method according to claim1, in which the output flow is generated with at least one flow outputdevice (20, 30, 40, 50 a, 50 b) with at least one output channel (16 a,16 b, 25 a, 25 b, 34, 42 a, 42 b) which opens into the discharge channelor at the end of the discharge channel (14, 21, 31, 41, 51).
 3. Themethod according to claim 1 or 2, in which a flow velocity of the outputflow is established with the flow output device (20, 30, 40, 50 a, 50b), this flow velocity being lower than the flow velocity of the fluidin the discharge channel.
 4. The method according to claim 1 or 2, inwhich a flow velocity of the output flow is established with the flowoutput device (20, 30, 40, 50 a, 50 b), this flow velocity being higherthan the flow velocity of the fluid in the discharge channel.
 5. Themethod according to one of the preceding claims, whereby a dischargeflow is formed with the flow output device (20, 30, 40, 50 a, 50 b), thedensity or concentration of the microparticles in this discharge flowbeing lower than that in the initial fluid flow.
 6. The method accordingto claim 1, whereby the discharge flow comprising the fluid flow and thefirst output flows (54 b, c) is merged with additional output flows (54b, c) and delivered through a conduction element.
 7. The methodaccording to one of the preceding claims, whereby at least one treatmentsolution for treating the microparticles is used to form the outputflow.
 8. The method according to one of the preceding claims, wherebysingle-cell deposition is accomplished in a measurement, manipulation orstorage device, wherein a certain quantity of fluid is provided for eachmicroparticle with the output flow, this quantity being transferred as adrop containing the microparticle to the measurement, manipulation orstorage device.
 9. The method according to claim 8, in which asingle-cell deposition on a titer plate or a cell culture plate isperformed.
 10. The method according to one of the preceding claims,whereby manipulation and/or characterization of the microparticles isperformed in the fluidic microsystem before discharge of the fluid flowwith the suspended microparticles.
 11. The method according to one ofthe preceding claims, whereby the microparticles are biological cells orcell constituents, synthetic particles, macromolecules and/ormacromolecular aggregates.
 12. A fluidic microsystem (10) which has achannel arrangement (12) for receiving and/or continuous flow of fluidswith suspended microparticles (21 a) and at least one discharge channel(14, 21, 31, 41, 51) for guiding a fluid flow, characterized by at leastone flow output device having at least one output channel (16 a, 16 b,25 a, 25 b, 34, 42 a, 42 b) for guiding at least one output flow (24,44, 54 a-d), whereby the output channel opens at the end of thedischarge channel.
 13. A microsystem according to claim 12, whereby theoutput channel and the discharge channel converge into a conductionelement (19, 26, 35, 45, 55 a, 55 b) for guiding a discharge flow fromfluid and output flows to an outlet (15, 27, 32, 46, 52).
 14. Themicrosystem according to claim 13, whereby several flow output devices(50 a, 50 b) are provided successively downstream on the dischargechannel (51) or on the conduction element (55 a).
 15. The microsystemaccording to one of claims 12 through 14, whereby each output channel isoriented so that the output flow and the fluid flow run at an angle ofless than 90° to one another.
 16. The microsystem according to one ofclaims 12 through 15, whereby each output channel has a curved shape atwhose end the output channel opens convergently into the dischargechannel.
 17. The microsystem according to one of claims 12 through 16,whereby an output channel (34) is provided, opening at one side of theend of the respective discharge channel (31).
 18. The microsystemaccording to one of claims 12 through 16, whereby two output channels(16 a, 16 b, 25 a, 25 b, 42 a, 42 b) are provided, opening at the end ofthe discharge channel (14, 21, 41) from two opposite sides.
 19. Themicrosystem according to claim 17, whereby the two output channels (42a, 42 b) form asymmetrically shaped channel arcs relative to thedischarge channel (41).
 20. The microsystem according to one of claims12 through 19, whereby the flow output device has a pump device with acontrollable pump rate.
 21. The microsystem according to claim 20,whereby the pump device is based on the application of hydrostaticpressure.
 22. The microsystem according to one of claims 12 through 21,whereby the flow output device has at least one reservoir with treatmentsolutions.
 23. The microsystem according to claim 22, whereby thetreatment solutions include washing solutions, conservative solutions,culture media and/or cryoconservative solutions.
 24. The microsystemaccording to one of claims 12 through 23, whereby the channelarrangement is part of a solid-state chip to which the flow outputdevice is detachably attached.
 25. A flow output device consisting of acomponent which is attachable in a liquid tight connection to a fluidicmicrosystem for discharging suspended microparticles with at least oneoutput channel (16 a, 16 b, 25 a, 25 b, 34, 42 a, 42 b) which has firsta free end and secondly a connection for a pump device and/or areservoir with treatment solutions.